Add support for tracing vmap in pre-dispatch export (#154650)

Summary: ONNX team and recent transformer upgrade ran into this error and we also ran into during our export benchmarking. This diff makes it possible to trace through vmap implementation in pre-dispatch IR. Note that we don't support serializing functorch ops in pre-dispatch IR and in the future, we should desugar them to post-grad ops.

The implementation strategy is:
1. We add python wrappers around vmap APIs so that we attach custom torch function handler that is only on during non-strict export. The reason is we don't want to add this to default torch_function handler because it will break BC.
2. Some dynamo changes to make sure it picks up new python wrapper APIs. The reason is when we do strict export, we need to re-materialize these APIs in pre-dispatch IR from torch IR. We can avoid this by special casing in dynamo for export to proxy different API calls but i feel that is too much chaos because you need to be able to proxy 2 different variants of same vmap API.

Test Plan: CI

Differential Revision: D75623875

Pull Request resolved: https://github.com/pytorch/pytorch/pull/154650
Approved by: https://github.com/ezyang, https://github.com/zou3519

.flake8

@@ -48,6 +48,7 @@ per-file-ignores =
     torch/__init__.py: F401,TOR901
     torch/_custom_op/impl.py: TOR901
     torch/_export/serde/upgrade.py: TOR901
+    torch/_functorch/predispatch.py: TOR901
     torch/_functorch/vmap.py: TOR901
     torch/_inductor/test_operators.py: TOR901
     torch/_library/abstract_impl.py: TOR901